Device for heating dielectric materials coating an electricity conducting element by means of hyperfrequence waves

ABSTRACT

A device for heating dielectric materials coating an electricity conducting element by means of hyperfrequency waves comprising a tubular conducting casing closed at both ends by conducting members, two aligned tubular conducting cores separated by a space coaxially disposed inside said tubular casing thus forming a coaxial guide, the dielectric material covering the conductive element being made to pass inside said two spaced tubular cores, a generator connected to said coaxial guide producing hyperfrequence waves applied on the dielectric element on the space between said tubular cores.

O United States Patent [1113,553,413

[72] Inventor .lol Henri Auguste Soulier [56] References Cited 81 Boulevard Marceau, Colombes France NIT N pp No. 810,992 U ED STATES PATE TS [221 Filed Man 1969 3,457,385 7/1969 Cumming 2l9/l0.6l 3,46l,26l 8/1969 Lewisetal... 219/l0.55 [45] Patented Jan. 5, I971 [32] Priority Man 29 1968 3.465,] 14 9/1969 Bleackley 219/1055 [33] France Primary Examiner.l. V. Truhe [3]] No. 146502 Assistant ExaminerL. H. Bender AtI0rney-lrving M. Weiner [54] DEVICE FOR HEATING DIELECTRIC MATERIALS COATING AN ELECTRICITY CONDUCTING ABSTRACT: A device for heating dielectric materials coating f f eg BY MEANS OF HYPERFREQUENCE an electricity conducting element by means of hyperfrequency 7 Cl 3 D i Fi waves comprising a tubular conducting casing closed at both aims raw ng ends by conducting members, two aligned tubular conducting [52] U.S. CI 219/10.55, cores separated by a space coaxially disposed inside said tubu- 219/10.6l lar casing thus forming a coaxial guide, the dielectric material [5]] Int. Cl H05b 9/00, covering the conductive element being made to pass inside H05b 5/00 said two spaced tubular cores, a generator connected to said [50] Field of Search 210/1055, coaxial guide producing hyperfrequence waves applied on the 10.61 dielectric element on the space between said tubular cores.

PATENTEB JAN 5 SHEET 1 OF 2 PATENTEBJAN 5197: 35533113 SHEET 2 [IF 2 F i a6.

. DEVICE FOR HEATING DIELECTRIC MATERIALS COATING AN ELECTRICITY CONDUCTING ELEMENT BY MEANS OF I-IYPERFREQUENCE WAVES The continuous vulcanizing of dielectric coatings of various conductive shieldings, such as dielectric coatings, enclosing electricity conductor cables raises serious problems. Actually,

the coating must be heated to be vulcanized in the case of elastomers, or be completely reticulated in the case of thermoplastic resins to which reticulating media, such as peroxides, are added.

Up till now, for effecting this heat treatment steam or gas pressure heaters have been used, the steam or gas forming the medium transmitting the heat to the dielectric coatings. Due to the poor heat conducting nature of these coatings it is obviously necessarythat said pressure heaters be of great length so that the treatment is evenly distributed over the entire thickness of said coating, while enabling a continuous advance of the article under treatment.

, Machines making the depositing of dielectric coatings possible on conductor cables or metal shields other than electric conductors are capable of operating continuously at high speed. These machines are not made the best use of, or else, it is necessary that the pressure heaters with which they cooperate must be extremely long, which involves considerable investments.

Up till now, it has, however, not been possible to substitute devices for said pressure heaters enabling hyperfrequency waves to be used, because the existing hyperfrequency furnaces are formed by resonant or guided cavities and the presence of metal within the dielectric so affected the characteristics of these furnaces that it was impossible to obtain a regular heating of the dielectric coating the conductor.

The present invention creates anew device which enables continuous and very high speed treatment of metal elements, particularly of electric cables, coated with dielectric material that is to be subjected to heat treatment.

According to the invention, the device comprises a tubular conducting casing closed at both ends by conducting members, at least two aligned tubular conducting cores, separated from each other by a space, being fixedly arranged inside said casing and coaxially with it for making a coaxial conductor, the dielectric material coating a conductor being made to circulate inside said two tubular cores for being subjected to an electric field created by hyperfrequency waves produced from a generator connected to said coaxial conductor, which form the casing and cores, by an electronic adapter assembly, so that the electric field produced between the conducting casing and said cores is applied on the dielectric in the space separating said cores.

Embodiments of the invention are shown, by way of non restrictive example, in the accompanying drawing.

FIG. I is a partly diagrammatical elevation section of the device of the invention.

FIG. 2 is an electrical diagram of the device of FIG. 1.

FIG. 3 is an elevation section similar to FIG. 1, showing an alternative embodiment of the device.

The invention relates to a device for vulcanizing elastomers or reticulating particular thermoplastic synthetic resins coating a wire or conductor cable 1, these coating elastomers or resins being designated by 2, the cable 1 is preferably placed in line with the coating device shown in the drawing by the nose of a slubber which has a bore 3 for the passage of a wire or cable 1, admission ducts 4 for the coating 2 in the form of lugs, and a calibration jet 5. The calibration jet 5 can obviously be made in numerous different manners according to whether the coating 2 must have smooth or longitudinally or transversally grooved walls, or whether this coating must be made adherent over the entire surface of the wire or cable 1, or, on the contrary, that this coating be separate from said wire or cable, or that it should only be in mutual contact at certain points, which, if so required, necessitates the jet 5 being provided with shaping fixed or movable dies and that these dies cooperate with mechanisms setting up a pressure or depression inside and/or outside the coating 2. Likewise, the

jet 5 can be placed immediately at the entry to the device of the invention, or on the contrary, be separated from it for a certain distance, which depends on supplementary treatments that may be required to be put into operation.

The device of the invention itself is intended to heat or reheat the coating material 2 so as to bring it to a suitable temperature for vulcanizing in the case of elastomers, or for reticulating in the case of thermoplastic resins such as reticualted polyethylenes, that is to say, containing peroxides, for instance. In the case of rubber, the coating 2 should be raised to a temperature of about C.

As shown by the drawing, the device uses a hyperfrequency wave generator designated by 6, which is formed by a magnetron whose antenna 7 is placed in a rectangular section wave guide 8 made of conductive metal, such as brass, copper, aluminum, etc. The wave guide 8 communicates with and is connected to a casing 9 of annular section. The casing 9 contains at least two tubular members or cores l0 and 1] arranged concentrically to said casing so that said casing and said tubular members l0, 11 form a coaxial conductor. The ends of the wave guide 8 p are provided with short circuit buttons 12, 13 and likewise the ends of the casing 9 are provided with short circuit rings 14 and 15. Rings 16 and 17 of material pervious to hyperfrequency waves, such as tetrafluorethylene, are slipped on the cores 10, 11 on either side of a coaxial chamber 18 confined between the ends opposite to these cores. The rings 16, 17 are preferably movable axially, and to this end, are connected to operating members 19, which may be metallic for instance, and cover at least part of slots 20 provided in the casing 9.

The conductor cable 1 provided with its coating 2 is made to pass inside the tubular cores l0 and 11. It is advantageous that the internal diameter of said tubular cores should be close to the external diameter of the covered cable I, and moreover, it is important that no friction should exist between the coating 2 and the inner wall of the cores 10, 11. To this end, sheathing 21 is advantageously provided inside the cores 10, II, this sheathing being made of a material with a low friction coefficient and not affected by hyperfrequency waves and the electric fields arising therefrom, for example also of polytetrafluorethylene. By providing sets of sheathing 21 of various thicknesses and by fitting this sheathing in a removable manner in the tubular cores I0, 11, it becomes possible to operate cables with various diameter coverings without altering the device of the invention.

The drawing does not show the device for hauling the cable, but it is obvious that such device can be provided so that the cable can remove continuously and at a steady speed in the device of the invention.

As is known in hyperfrequency technique, it is essential to match in all the active parts of the device the impedance of the wave generator, namely of the magnetron 6. Consequently, it is necessary in the first place to electronically adapt the generating part comprising the magnetron, the wave guide and a part of the coaxial conductor forming the casing 9 and tubular core 10.

It is known that the waveguide 8 can be shown in electric equivalence by an RLC circuit, i.e., an inductance-capacityresistance circuit of the same characteristic impedance as the magnetron. The coating part 2, which extends in the coaxial chamber 18 separating the two cores l0, 11, forms a load C,,, because this part absorbs the power transmitted by the magnetron 6 in electromagnetic form. Consequently, it is advisable to effect an adaptation so that the impedance belonging to the load C,, is the same as the characteristic impedance of the magnetron, shown in FIGQZ by an impedance transformer T whose secondary is in series with the load CThe adaptation to the characteristic impedance of the magnetron is done by the rings 16, 17 which act as an assembly ofcapacitors and self-inductances coupled with the load CAs explained in the foregoing, the rings 16, 17 are movable and consequently act as a variable capacitor-inductance assembly as shown at L,, C, in FIG. 2.

The coaxial conductor made by the casing 9 and tubular core 10 forms a kind of transmission line between the RLC circuit and the transformer T. The impedance of the line must thus be adjustable, which is obtained by making at least some of the short circuit buttons l2, 13 or l4, l movable, which consequently act as inductances L and variable capacities C mounted in series in the secondary circuit of the transformer T.

it is well known in hyperfrequency wave technique that in a coaxial conductor, such as that formed by the casing 9 and tubular cores l0 and 1 l, the electric field between the two coaxial elements is shown in the manner diagrammatized by the arrows in FIG. 1. Consequently, this high frequency field, in the region of 2,500 mc./s, is absorbed by the dielectrics, particularly the dielectrics of the kind forming the coating 2 of the cable I, in the area where this coating is free inside the casing 9. Of course, the width of the coaxial chamber 18, i.e., the distance separating the cores l0 and 11, is not immaterial, this width particularly depending on the frequency used and the thickness of the coating 2 to be treated. As an example, the distance separating the cores and 11 can be about 2 cm. for treating a coating of cables of 10 to 60 mm. diameter in a device dispersing a power of about 2 kw whose external casing 9 has a length of between 250 and 500 mm and a diameter of 50 to 80 mm.

As an example, a 6.5 mm diameter metal cab core cable, coated with synthetic material up to 20.5 mm. can be treated with an oven of the following characteristics:

Cutout impedance Z 65 Ohms;

Thickness of the polytetrafluorethylene buttons l6, 17 for adapting the impedance: 3 mm., interior guides 10 and 11 of 21 X 26 mm. diameter;

exterior guide 9 of65 X 70 mm. diameter.

Another example can be a 9 mm. diameter metal core cable coated with synthetic material up to 12.5 mm. can be treated with oven having the following characteristics:

Cutout impedance Z N0 Ohms;

Thickness of the polytetrafluorethylene buttons l6, 17 for adapting the impedance 13.3 mm.;

interior guides 10 and 11 of 13 16 mm. diameter;

exterior guide 9 of 40 X 50 mm. diameter.

in the foregoing the device comprises a rectangular wave guide and a coaxial type conductor. However, this arrangement is not compulsory, and FIG. 3 shows that the wave guide can be replaced by two coaxial conductor segments 22, 22a and 23, 23a respectively connected to the casing 9 and tubular core 10, the magnetron 6 being, in this case, directly connected to the coaxial conductors 22, 22a, while a short circuit button 13a is provided to enable the electronic adaptation of the device whose other parts remain similar to those described in the foregoing with reference to H6. l.

The invention is not restricted to the embodiments shown and described in detail for various modifications can be applied thereto without going outside its scope. In particular, several devices similar to those described above can be arranged in series when it is necessary to develop a high power. Likewise, said devices can be filled with particular gases. other than air; for instance, for treating reticulated thermoplastic resins, it is advantageous to use nitrogen.

lclaim: I 1. Device for curing by means of hyperfrequency waves a dielectric material of an insulated wire or cable which is moved continuously, comprising, in combination: a tubular casing made of an electrically conductive material and at least partially closed at bo I fits ends by electrically conductive rings; t at least two aligned tubes made of electrically conductive material which are disposed in a parallel'fashio'n inside or said tubular casing and which are separated by a predetermined space; at least two insulating rings substantially parallel to said electrically conductive rings and being made of a material which is pervious to hyperfrequency waves, said insulatmg rings cooperating with said electrically conductive rings to support said tubes whereby said tubes form a coaxial guide with said tubular casing; and

a generator of hyperfrequency waves operatively connected to said coaxial guide for producing an electric field therein, whereby said dielectric material of said insulated wire or cable when moving through said tubes and guided therein is subjected to said electric field only in said predetermined space which separates said tubes.

2. Device according to claim 1, including a rectangular wave guide which is connected to said tubular casinggand an antenna operatively connected to said generator and being at least partially disposed within said rectangular waveguide to facilitate transmission of said electric field to said coaxial guide 3. Device according to claim l, wherein the internal surfaces of said aligned tubes are covered with a material which is pervious to said hyperfrequency waves and which has a substantially low coefficient of friction, such as polytetrafluorethylene. v

4. Device according to claim 1, including twosections' of coaxial conductors connected to said tubular casingand one of said aligned tubes to facilitate transmission of said electric field to said coaxial guide.

5. Device according to claim 2, wherein said rectangular wave guide is provided at its ends with short circuit buttons for effecting an electronic 'matching oradaptation of the device to the impedence ofsaid generator of hyperfrequency waves. 7

6. Device according to claim 1 in which means are provide to move said insulating rings of material pervious to hyperfrequency waves for effecting the adaptation of the impedenc'e of the load, formed by the portion of said dielectric material which is subjected to said electric field, to the impedance of said generator of hyperfrequency waves.

7. Device according to claim 6 in which said insulating rings are made at least partially of polytetrafluorethylene. 

1. Device for curing by means of hyperfrequency waves a dielectric material of an insulated wire or cable which is moved continuously, comprising, in combination: a tubular casing made of an electrically conductive material and at least partially closed at both of its ends by electrically conductive rings; at least two aligned tubes made of electrically conductive material which are disposed in a parallel fashion inside of said tubular casing and which are separated by a predetermined space; at least two insulating rings substantially parallel to said electrically conductive rings and being made of a material which is pervious to hyperfrequency waves, said insulating rings cooperating with said electrically conductive rings to support said tubes whereby said tubes form a coaxial guide with said tubular casing; and a generator of hyperfrequency waves operatively connected to said coaxial guide for producing an electric field therein, whereby said dielectric material of said insulated wire or cable when moving through said tubes and guided therein is subjected to said electric field only in said predetermined space which separates said tubes.
 2. Device according to claim 1, including a rectangular wave guide which is connected to said tubular casing; and an antenna operatively connected to said generator and being at least partially disposed within said rectangular wave guide to facilitate transmission of said electric field to said coaxial guide.
 3. Device according to claim 1, wherein the internal surfaces of said aligned tubes are covered with a material which is pervious to said hyperfrequency waves and which has a substantially low coefficient of friction, such as polytetrafluorethylene.
 4. Device according to claim 1, including two sections of coaxial conductors connected to said tubular casing and one of said aligned tubes to facilitate transmission of said electric field to said coaxial guide.
 5. Device according to claim 2, wherein said rectangular wave guide is provided at its ends with short circuit buttons for effecting an electronic matching or adaptation of the device to the impedence of said generator of hyperfrequency waves.
 6. Device according to claim 1 in which means are provide to move said insulating rings of material pervious to hyperfrequency waves for effecting the adaptation of the impedence of the load, formed by the portion of said dielectric material which is subjected to said electric field, to the impedence of said generator of hyperfrequency waves.
 7. Device according to claim 6 in which said insulating rings are made at least partially of polytetrafluorethylene. 